Diffusion in mercury cadmium telluride—an update

Abstract

The various diffusion coefficients (self-diffusivity, chemical self-diffusivity compositional diffusivity, impurity diffusivity) are defined. The conditions required for the observation of a Kirkendall effect are described. There is good agreement in the results for Hg and for Cd self-diffusion. The evidence suggests that the self-diffusivity is largely independent of P_Hg above ~300°C but shows an increase as Hg saturation is approached (for both Hg and Cd). Good agreement is also found in the Arrhenius parameters describing the movement of the p to n conversion boundary. Modeling of this diffusion boundary does, however, raise problems which are discussed. The situation in compositional interdiffusion is more complex: above ~400°C, reasonable agreement exists between various workers for large x_Hg but not for small values; below 400°C, substantial disagreement is evident. In impurity diffusion exhibits both erfc and non-erfc profiles for reasons which are unclear. Good agreement is found between In diffusivity measurements at high In concentrations: at low concentrations, the diffusivity decreases dramatically. As diffusion yields erfc profiles with good agreement again being found: a notable feature is the P_Hg dependence of the As diffusivity. Where appropriate, diffusion models are discussed.